Lead-free ceramics of Na0.5K0.5Nb1-xSbxO3 (NKNS) and Na0.5K0.5Nb1-xSbxO3 + 0.5 mol%MnO2 (NKNS + 0.5 mol%MnO2) (0 < x < 0.06) ceramics were prepared by a conventional solid-state hot pressing method. The ceramics possess a single-phase perovskite structure with orthorhombic symmetry. Microstructural examination revealed that Mn doping of NKNS leads to improvement of densification. The cubic-tetragonal and tetragonal-orthorhombic phase transitions of NKNS shifted to higher and lower temperature, respectively after introduction of Mn ion. Besides, ferroelectric and piezoelectric properties were improved. The results were discussed in term of difference in both ionic size and electronegativity of Nb5+ and Sb5+ and improvement of densification after Mn ion doping.

Transparent Yb³⁺/Er³⁺glass-ceramic was successfully obtained by the extrusion method. The extrusion of oxyfluoride tellurite-germanate glass co-doped with Yb³⁺and Er³⁺ions at 520°C resulted in the formation of Ba_0:75Er_0:25F_2:25 nanocrystals, leading to an increase in the upconversion (UC) emission intensity of 35 times in glass-ceramic with respect to the glass. The glass to glass-ceramic transition was confirmed by X-ray diffraction (XRD) and Transmission electron microscope (TEM). Also, the structural changes that occurred during crystallization were assessed using Fourier-transform infrared (FTIR) spectroscopy. Furthermore, the pump power and temperature UC emission dependence of glass and glass-ceramic under 976 nm laser excitation were investigated in detail. The assessments showed that i) two-phonons are involved in the UC process and ii) the temperature has a significant influence over it. The Yb³⁺/Er³⁺ codoped glass-ceramic shows relatively high S_a and S_r values in a wide temperature range from 300 to 573 K, presenting the maximal S_a value of 3:50 x 10^–3 at 573 K and the maximal S_r value of 6:30 x 10^–3at 364 K. These results suggest that the glass-ceramic is a good candidate for optical applications such as luminescent thermometry.